Bisguanidinium dinuclear oxodiperoxomolybdosulfate ion pair-catalyzed enantioselective sulfoxidation

Catalytic use of peroxomolybdate for asymmetric transformations has attracted increasing attention due to its catalytic properties and application in catalysis. Herein, we report chiral bisguanidinium dinuclear oxodiperoxomolybdosulfate [BG](2+)[(μ-SO(4))Mo(2)O(2)(μ-O(2))(2)(O(2))(2)](2−) ion pair, as a catalyst for enantioselective sulfoxidation using aqueous H(2)O(2) as the terminal oxidant. The ion pair catalyst is isolatable, stable and useful for the oxidation of a range of dialkyl sulfides. The practical utility was illustrated using a gram-scale synthesis of armodafinil, a commercial drug, with the catalyst generated in situ from 0.25 mol% of bisguanidinium and 2.5 mol% of Na(2)MoO(4)·2H(2)O. Structural characterization of this ion pair catalyst has been successfully achieved using single-crystal X-ray crystallography.